I agree that after Black Plague there isn't much to tell that would fit the Penumbra games. I really liked the ending of Black Plague.

I'd say Requiem does add a kind of closure, that is, if you ''choose'' a canon ending. Penumbra is about Phillip, trying to find out what happened to his father, as well as about the shelter and Tuurngait. It does give closure about Phillips fate.